In recent years, the dairy industry has seen a drastic decrease in the reproductive efficiency of cows. This is reflected in undesirable decreases in such industry-standard reproductive performance measurements as (1) days to first service, (2) days to conception, (3) calving interval, (4) services per conception, (5) non-return rate, (6) estrus (or “heat”) detection rate, and (7) pregnancy rate. Estrus, or heat, detection, in particular, is useful for identifying cows that are likely to become pregnant if inseminated at the time of estrus detection, or shortly thereafter. Wrongly identifying a cow as not being “in heat” (i.e., “estrus-negative”) is a significant contributor to reproductive inefficiency. This has a corresponding significant impact on the dairy industry because dairy cows that are not reproductively efficient are culled.